This invention relates to an aqueous emulsion composition of a fluorochemical (meth)acrylate copolymer for imparting a highly-durable oil and water repellent finish to textiles, wherein the copolymer imparts little or no yellowing of the textiles upon curing. In all instances herein, the term xe2x80x9c(meth)acrylatexe2x80x9d is used to denote either acrylate or methacrylate, or mixtures thereof.
Fluoropolymer compositions having utility as textile treating agents, generally contain pendant perfluoroalkyl groups of three or more carbon atoms, which provide oil- and water-repellency when the compositions are applied to fabric surfaces. The perfluoroalkyl groups are attached by various connecting groups to polymerizable groups not containing fluorine. The resulting monomer is then generally copolymerized with other monomers which confer additional favorable properties to the textile fabrics. The polymer chain backbone of the resulting copolymer may be (meth)acrylates, vinyl, vinylidene or other groups. They may act to extend the performance of the more expensive perfluoroalkyl groups, or act as bonding agent to fix the copolymer to the fabric, or may serve other functions. Generally, such copolymers are prepared by copolymerization of two or more monomers in an aqueous media stabilized with a surfactant.
These polymers are marketed as aqueous emulsions for easy application to the fabric. The fabric-treating composition may also include other additives in addition to those copolymerized with the fluoromonomer. In particular, various compounds such as blocked isocyanates are frequently added before or after polymerization to promote durability of a desired property such as repellency. In this usage, the blocking agent is removed from the isocyanate under the thermal conditions used when curing the treated fabric, allowing the isocyanate group to interact with the fabric and improve the desired durability.
Typically, the major monomers used for such copolymers include a perfluoroalkyl (meth)acrylate and a long-chain alkyl (meth)acrylate such as stearyl (meth)acrylate. Many such copolymers also contain vinyl or vinylidene chloride in order to improve the durability of the repellency treatment. Smaller amounts of various specialized monomers containing hydroxyl groups and/or alkylene oxide oligomers may be incorporated to impart improved cross-linking, latex stability and/or substantivity. Each ingredient may impart some potentially undesirable properties in addition to its desirable ones.
For example, U.S. Pat. No. 4,742,140 discloses a composition comprising by weight 40-75% of a specific perfluoroalkylethyl acrylate mixture, 10-35% vinylidene chloride and 10-25% alkyl (meth)acrylate having an alkyl chain length of 2-18 carbons. A preferred composition consists essentially of by weight 45-70% of the above perfluoroalkylethyl acrylate, 15-30% vinylidene chloride, 10-20% of the above alkyl (meth)acrylate, 0.1-2% N-methylol acrylamide, and optionally up to 5% chlorohydroxypropyl (meth)acrylate, and up to 5% poly(oxyethylene) (meth)acrylate. Improved repellency and durability are claimed over prior art compositions.
However, polymers containing such large amounts of vinylidene chloride may cause yellowing of the fabric upon curing, due to dehydrohalogenation of the vinylidene chloride. There is a need for compositions which impart a highly durable repellency to fabrics but which contain less than 10% by weight of vinylidene chloride. There is also a need for compositions having durable repellency properties but which require less fluorine to be present. The present invention provides such compositions.
The present invention comprises a copolymer composition, which imparts a highly durable, low yellowing repellent finish to fabrics and fabric blends comprising monomers copolymerized in the following percentages by weight:
(a) from about 40% to about 75% of a monomer of formula I:
Rfxe2x80x94CH2CH2xe2x80x94OC(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83I
(b) from about 15% to about 55% of a monomer of formula II:
R2xe2x80x94OC(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83II
(c) from 1.5% to about 5% of a monomer of the formula III:
HOxe2x80x94CH2CH2xe2x80x94OC(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83III
(d) from 1.5% to about 5% of a monomer of the formula IV:
Hxe2x80x94(OCH2CH2)mxe2x80x94Oxe2x80x94C(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83IV
(e) from 1% to about 3% of a monomer of the formula V:
HOxe2x80x94CH2xe2x80x94NHxe2x80x94C(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83V
wherein Rf is a straight or branched-chain perfluoroalkyl group of from 2 to about 20 carbon atoms, each R is independently H or CH3; R2 is an alkyl chain from 2 to about 18 carbon atoms; and m is 2 to about 10.
Optionally, the copolymer composition may also contain:
(f) from 0% up to about 9.8% of vinylidene chloride (formula VI) or vinyl acetate (formula VII), or a mixture thereof:
CH2xe2x95x90CCl2xe2x80x83xe2x80x83VI
CH 3xe2x80x94(O)COCHxe2x95x90CH2xe2x80x83xe2x80x83VII
(g) from 0% to about 2% of a blocked isocyanate such as the monomer of the formula VIII:
(CH3)(CH2CH3)Cxe2x95x90Nxe2x80x94Oxe2x80x94C(O)xe2x80x94NHxe2x80x94CH2xe2x80x94CH2xe2x80x94OC(O)C(R)xe2x95x90CH2xe2x80x83xe2x80x83VIII
wherein R is H or CH3.
The present invention further comprises a method of treating a fabric or fabric blend to impart oil and water repellency comprising application to the surface of the fabric or fabric blend of the composition as described above, and the fabric or fabric blend which has been so treated. The treated fabric or fabric blend has a fluorine content of from about 0.05% to about 0.5% by weight.
Trademarks and tradenames are indicated herein by capitalization. This invention comprises improved fluorochemical copolymers useful for imparting repellent properties to fabrics or blends. By xe2x80x9cfabricsxe2x80x9d is meant natural or synthetic fabrics composed of fibers of cotton, rayon, silk, wool, polyester, polypropylene, polyolefins, nylon, and aramids such as xe2x80x9cNOMEXxe2x80x9d and xe2x80x9cKEVLAR.xe2x80x9d By xe2x80x9cfabric blendsxe2x80x9d is meant fabric made of two or more types of fibers. Typically these blends are a combination of a natural fiber and a synthetic fiber, but also can include a blend of two natural fibers or of two synthetic fibers. Superior repellent properties, along with desirable properties of low yellowing and good durability are imparted to fabrics and fabric blends by the addition of these improved fluorochemical copolymers. They are applied to the fabric in the form of a dispersion in water or other solvent, either before, after, or during the application of other fabric treatment chemicals.
The copolymers of this invention are prepared by conventional emulsion polymerization techniques. The surfactant employed to stabilize the emulsion during its formation and during polymerization can be a cationic or non-ionic emulsifying agent or agents. The polymerization is conveniently initiated by azo initiators such as 2,2xe2x80x2-azobis(2-amidinopropane) dihydrochloride. These initiators are sold by E. I. du Pont de Nemours and Company, Wilmington, Del., commercially under the name of xe2x80x9cVAZOxe2x80x9d, and by Wako Pure Industries, Ltd., Richmond, Va., under the name xe2x80x9cV-50.xe2x80x9d
The emulsions produced are applied to textile surfaces by known methods to impart oil-, soil- and water-repellency. The copolymers are applied to the fabric or fabric blend either alone or in a mixture with other textile treatment agents or finishes. A distinguishing feature of the fluoropolymers of the present invention is their effectiveness at low application levels, low yellowing of the fabric upon curing, and high durability of the finish on the fabric.
The highly efficient copolymers discussed above are characterized in that they contain copolymerized comonomers in the following percentages by weight, relative to the total weight of the copolymers:
(a) from about 40% to about 75% of a monomer of formula I:
Rfxe2x80x94CH2CH2xe2x80x94OC(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83I
(b) from about 15% to about 55% of a monomer of formula II:
R2xe2x80x94OC(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83II
(c) from 1.5% to about 5% of a monomer of the formula III:
HOxe2x80x94CH2CH2xe2x80x94OC(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83III
(d) from 1.5% to about 5% of a monomer of the formula IV:
Hxe2x80x94(OCH2CH2)mxe2x80x94Oxe2x80x94C(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83IV
(e) from 1% to about 3% of a monomer of the formula V:
HOxe2x80x94CH2xe2x80x94NHxe2x80x94C(O)xe2x80x94C(R)xe2x95x90CH2xe2x80x83xe2x80x83V
wherein Rf is a straight or branched-chain perfluoroalkyl group of from 2 to about 20 carbon atoms, each R is independently H or CH3; R2 is an alkyl chain from 2 to about 18 carbon atoms; and m is 2 to about 10. The comonomers are combined in proportion within their designated ranges to add up to 100% by weight.
While the majority of the fluoropolymer repellents described in the literature today contain both a perfluoroalkyl (meth)acrylate and a long-chain alkyl (meth)acrylate, traditionally the ratio of these two monomers has been 75-60% fluoromonomer to 15-30% alkyl monomer. With the proportion of monomers in the present invention as described above, a highly durable repellent finish may be developed using only about a 50/50 ratio of these two monomers, greatly increasing fluorine efficiency. The high durability and repellency is obtained through a careful balance of monomers, specifically the incorporation of the three cross-linking monomers (c), (d) and (e), in spite of the reduction or removal of a vinylidene chloride component. This invention discloses the surprising benefits to be obtained using all three monomers (c), (d) or (e) in the proportions described above in combination with the elimination or reduction of the amount of vinylidene chloride.
Preferably monomer (a) of formula I is a perfluoroalkylethyl acrylate with a perfluoroalkyl carbon chain length distribution by weight of about 50% of 8-carbon, about 30% of 10-carbon, about 10% of 12-carbon, and with smaller percentages of 6-carbon and 14-carbon and longer chain lengths. The proportion of monomer (a) of formula I is at least about 40% relative to the total weight of copolymer. If it is present in lower amounts, the polymer becomes more hydrophilic and the oil- and water-repellency drops off to an undesirable level. The proportion of monomer (a) of formula I is less than about 75%. If it is present in higher amounts, the polymer is no longer cost effective. The proportion of monomer (a) of formula I in the copolymer is preferably between about 40% and about 60% by weight for application to synthetic fabrics, and from about 55% to about 75% by weight for application to cotton fabrics. These ranges are preferred for the best durability of oil-, water- and soil repellent properties in currently envisioned applications of treatment of fabrics and fabric blends. Other proportions may be more desirable for other applications.
The required monomer (b) of formula II in the present invention is one or a mixture of alkyl (meth)acrylates having chain lengths of 2 to 18 carbons, preferably 12 to 18 carbons. These are added to the polymerization in proportions from 15% to about 55%. Preferably the proportion of monomer (b) in the copolymer is between about 35% and about 55% by weight for application to synthetic fabrics, and about 15% to about 35% by weight for application to cotton fabrics. As used herein, xe2x80x9calkylxe2x80x9d refers to linear, branched-chain and cyclic alkyl groups. Examples of such monomers include ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, stearyl acrylate, lauryl acrylate, stearyl methacrylate, lauryl methacrylate, 2-ethylhexyl acrylate, and isodecyl acrylate. Of the foregoing, stearyl acrylate and stearyl methacrylate are most preferred.
It has found that by incorporating the three monomers (c), (d) and (e) of formulas II, IV and V into the fluorinated polymer, the amount of vinylidene chloride can be sharply decreased or eliminated while achieving comparable repellency and durability. Monomer (c) is a hydroxyethyl (meth)acrylate. Preferably it is hydroxyethyl methacrylate (HEMA). Monomer (d) is an ethoxylated (meth)acrylate wherein the number of ethoxy groups is between 2 and 10. Between 5 and 10 ethoxy groups are preferred. Monomer (e) is N-methylol acrylamide or methacrylamide. N-methylol acrylamide (MAM) is preferred.
The proportion of each of these monomers employed determines the softness of the product, the performance of the product across several substrates and the durability of the repellency properties. The proportion of each of these monomers must be at least 1.5% by weight of the copolymer to provide the necessary durability and performance attributes. The percentage by weight of monomer (c) and (d) must each be below about 5% by weight, and the percentage by weight of monomer (e) must be below about 3% by weight. The utility of incorporating these three monomers into the polymer backbone is the efficient cross-linking between the various polymer chains upon cure. The cross-linking efficiency between polymer chains is especially important when dealing with synthetic fabrics where reactive groups on the surface may be at a very low concentration. In this case the durability of the finish would arise from the polymers linking around the individual fibers and thus be physically trapped rather than chemically bound to the fibers.
One of the major advantages of the inventive composition is its flexibility for a variety of uses. Its hydrophobic and oleophobic properties on a wide range of fabrics can be varied for different applications by simply varying the relative amounts of monomers (a) (b) (c) (d) and (e), while still maintaining its properties as a durable, low yellowing repellent.
Optionally, the copolymer composition can also contain up to about 9.8% by weight of monomer (f); i.e., vinylidene chloride (formula VI) or vinyl acetate (formula VII), or a mixture thereof:
CH2xe2x95x90CCI2xe2x80x83xe2x80x83VI
CH3xe2x80x94(O)COCHxe2x95x90CH2xe2x80x83xe2x80x83VII
The addition of a relatively small amount of vinylidene chloride or vinyl acetate may be desirable to improve the compatibility of the copolymer with the fabric substrate, or to reduce overall costs. Preferably the amount of monomer (f) is below about 8% by weight, more preferably below about 5% by weight. To have a noticeable effect on compatibility, monomer (f) is present in a proportion of at least about 1%.
The repellent composition applied to the fabric may optionally contain a blocked isocyanate to promote durability, either as part of the copolymer or added after copolymerization. It has been found that the fabric""s hand is preferably soft if the blocked isocyanate is part of the copolymer. The desirability of adding a blocked isocyanate depends on the particular application for the copolymer. For most of the presently envisioned applications, it does not need to be present to achieve satisfactory cross-linking between chains or bonding to the fibers. However, for optimum durability in the application of the copolymer of this invention to cotton fabrics, it is preferred that up to 2% by weight be added. To have a noticeable effect on durability, it must be present in a proportion of at least about 1%. Optionally therefore, the copolymer composition may also contain up to about 2% by weight of monomer (g), a blocked isocyanate.
xe2x80x9cBlocked isocyanatexe2x80x9d is used herein to mean the reaction products of an isocyanate and a blocking agent, wherein the blocking agent is removable from the isocyanate under the thermal conditions employed upon curing a fabric treated with a compound containing the blocked isocyanate group. These are frequently used to add durability to certain properties of treated fabrics. Conventional blocking agents include aryl alcohols, alkanone oximes, aryl thioles, organic active hydrogen compounds, sodium bisulfite and hydroxylamine. Preferred blocking agents are alkanone oximes (ketoximes), which can be de-blocked at a relatively low temperature such as used during a typical fabric curing process. Particularly preferred is butanone oxime.
Many isocyanates are suitable for use in preparation of the blocked isocyanate including linear or branched isocyanates, aromatic isocyanates, and cyclic isocyanates. Preferred are linear or branches isocyanates. Especially preferred for use as the blocked isocyanate herein is the monomer, 2-(0-[1xe2x80x2-methyl-propylideneamino]carboxyamino)ethyl methacrylate, of formula VIII
(CH3)(CH2CH3)Cxe2x95x90Nxe2x80x94Oxe2x80x94C(O)xe2x80x94NHxe2x80x94CH2xe2x80x94CH2xe2x80x94OC(O)C(R)xe2x95x90CH2xe2x80x83xe2x80x83VIII
wherein R is H or CH3.
The present invention further comprises a method of treating fabrics or fabric blends comprising application to the surface of the fabric or fabric blend of an effective amount of a copolymer composition as described above, and the fabric or fabric blend so treated. The copolymers are applied to the fabric or blended fabric to be treated either alone or in a mixture with other textile treatment agents or finishes. The copolymers are generally applied to textile fabrics by spraying, dipping, padding, or other well-known methods. After excess liquid has been removed, for example by squeeze rolls, the treated fabric is dried and then cured by heating, for example, from 100xc2x0 C. to 190xc2x0 C., for at least 30 seconds, typically 60-180 seconds. Such curing enhances oil-, water- and soil repellency and durability of the repellency. While these curing conditions are typical, some commercial apparatus may operate outside these ranges because of its specific design features. The treated fabric has a fluorine content of from about 0.05% to about 0.5% by weight.
The present invention further comprises a fabric or fabric blend which has been treated to impart oil-and water-repellent properties thereto by application of an effective amount of a copolymer as described above. The treated fabric has a fluorine content of from about 0.05% to about 0.5% by weight. The treated fabric has superior oil-and water-repellencies, especially in terms of durability after washing, and decreased yellowing of the fabric.
The copolymers and method of the present invention are useful to enhance oil-, water- and soil-repellency of fabrics and fabric blends even after repeated laundering. The repellency property is durable, and is especially effective for synthetic fabrics. The treated fabrics and fabric blends of the present invention are useful in a variety of applications such as for textiles, clothing, furnishings and the like. The copolymers of the present invention are advantageous in that they give highly durable, low yellowing repellent finishes over a wide range of fabrics or fabric blends. The inventive compositions are made at lower materials cost than the current acrylate copolymers.
The following tests were employed in evaluating the examples herein.
Fabric Treatment
An aqueous bath containing 1.5% of the fluorinated product was used in all cases. The fabric was padded with the bath.
A. 100% Polyester and Blended Fabric
A wetting agent was also included in the bath at 0.2%. The fabric was cured at approximately 160xc2x0 C. for 2-3 minutes. The fabric was allowed to xe2x80x9crestxe2x80x9d after treatment and cure.
B. 100% Cotton Fabric
In most cases a resin such as Permafresh MSC was used. However in Example 6 and comparative Example B a wetting agent was found useful when used with a blocked isocyanate resin. The fabric was cured after treatment at approximately 150xc2x0 C. for 2-3 minutes. The fabric was allowed to xe2x80x9crestxe2x80x9d after treatment and cure.
Water Repellency
The water repellency of a treated substrate was measured according to the DuPont Technical Laboratory Method as outlined in the TEFLON Global Specifications and Quality Control Tests information packet. The test determines the resistance of a treated substrate to wetting by aqueous liquids. Drops of water-alcohol mixtures of varying surface tensions are placed on the fabric and the extent of surface wetting is determined visually. The test provides a rough index of aqueous stain resistance. A higher water repellency rating indicates a better resistance of a finished substrate to staining by water-based substances. The composition of standard test liquids is shown in the following table.
Water Repellencyxe2x80x94Spray Rating
Water repellency can be further tested by utilizing the spray test method. The treated fabric samples were tested for water repellency by following the AATCC standard Test Method No. 22-1996, conducted as follows. A fabric sample, treated with an aqueous dispersion of polymer as previously described, is conditioned for a minimum of 2 hours at 23xc2x0 C.+20% relative humidity and 65xc2x0 C.+10% relative humidity. The fabric sample is securely fastened on a plastic/metal embroidery hoop such that the fabric is wrinkle-free. The hoop is placed on the testing stand so that the fabric is facing up. Then 250 mL of water is poured into the testing funnel allowing the water to spray onto the fabric surface. Once the water has run through the funnel the hoop is rapped twice against the edge of a solid object with the fabric facing down. The spotted or wetted surface is compared with the AATCC standards found in the AATCC Technical Manual. The more wet the surface, the lower the number and the poorer the repellency. A 100 denotes no wetting, a 90 denotes slight wetting (three small spots), an 80 denotes wetting signified by several (10) spots at the spray points, a 70 denotes partial wetting of the upper fabric surface, a 50 denotes wetting of the entire upper fabric surface, a 0 denotes complete wetting of the lower and upper fabric surface.
Oil Repellency
The treated fabric samples were tested for oil repellency by a modification of AATCC standard Test Method No. 118, conducted as follows. A fabric sample, treated with an aqueous dispersion of polymer as previously described, is conditioned for a minimum of 2 hours at 23xc2x0 C.+20% relative humidity and 65xc2x0 C.+10% relative humidity. A series of organic liquids, identified below in Table 2, are then applied dropwise to is the fabric samples. Beginning with the lowest numbered test liquid (Repellency Rating No. 1), one drop (approximately 5 mm in diameter or 0.05 mL volume) is placed on each of three locations at least 5 mm apart. The drops are observed for 30 seconds. If, at the end of this period, two of the three drops are still spherical in shape with no wicking around the drops, three drops of the next highest numbered liquid are placed on adjacent sites and similarly observed for 30 seconds. The procedure is continued until one of the test liquids results in two of the three drops failing to remain spherical to hemispherical, or wetting or wicking occurs.
The oil repellency rating of the fabric is the highest numbered test liquid for which two of the three drops remained spherical to hemispherical, with no wicking for 30 seconds. In general, treated fabrics with a rating of 5 or more are considered good to excellent; fabrics having a rating of one or greater can be used in certain applications.
Yellowing of Fabric
The yellowing of a treated substrate upon cure was measured according to a DuPont Technical Laboratory Method. The method is as follows; a 2 inch by 2 inch (5.1 cm by 5.1 cm) piece of white polyester or cotton fabric is submerged into a neat solution of the product, removed and wrung out. The piece of fabric is then laid on a screen and cured in the oven at 180xc2x0 C. for 2-5 minutes. As a control, a piece of fabric is submerged in water and cured at 180xc2x0 C. The rating of the yellowing is done visually, the samples are compared and rated against themselves and the untreated cured substrate. A piece that does not yellow is rated as a 1-2; a piece that yellows slightly is rated as a 3-4; a piece that yellows and becomes slightly tan is rated as a 5-6; a piece that becomes yellow brown is rated as a 7-8; and finally a piece that becomes brown is rated as a 9-10.
Laundering Procedure
The fabric samples were laundered according to the U.S. Home Laundering Method outlined in the TEFLON Global Specifications and Quality Control Tests information packet. Fabric samples are loaded into a KENMORE automatic washer with a ballast load to give a total dry load of 4 lb. (1.0 kg). A commercial detergent is added (AATCC 1993 Standard Reference Detergent WOB) and the washer is filled to a high water level with warm water (105xc2x0 F.)(41xe2x96xa1C.). The samples and ballast are washed a designated number of times (5HW=5 washes, 10HW=10 washes, etc.) using a 12-minute normal wash cycle followed by rinse and spin cycles. The samples are not dried between wash cycles.
After washing is complete, the wet fabric samples and ballast are transferred to a KENMORE automatic dryer and dried for 45 minutes at the high/cotton setting to achieve a vent temperature of 155-160xc2x0 F. (68-71xc2x0 C.).